Method and apparatus to facilitate administering therapeutic radiation to a heterogeneous body

ABSTRACT

These teachings facilitate the administration of therapeutic radiation to a heterogeneous patient volume using a radiation beam source. More particularly, these teachings provide for determining a cross-sectional size of a radiation beam as corresponds to that radiation beam source and also for determining density information corresponding to the aforementioned heterogeneous body. These teachings then provide for generating a three-dimensional radiation dose calculation for the heterogeneous body using a control circuit configured as a convolution/superposition based dose calculator using a three-dimensional energy-spreading kernel. By one approach, these teachings provide for the calculator scaling total energy released per mass as a function of the cross-sectional size and energy of the radiation beam and the aforementioned density information.

TECHNICAL FIELD

These teachings relate generally to treating a patient's planning targetvolume with radiation pursuant to a radiation treatment plan and moreparticularly to generating a radiation treatment plan for that patient.

BACKGROUND

The use of radiation to treat medical conditions comprises a known areaof prior art endeavor. For example, radiation therapy comprises animportant component of many treatment plans for reducing or eliminatingunwanted tumors. Unfortunately, applied radiation does not inherentlydiscriminate between unwanted materials and adjacent tissues, organs, orthe like that are desired or even critical to continued survival of thepatient. As a result, radiation is ordinarily applied in a carefullyadministered manner to at least attempt to restrict the radiation to agiven target volume. A so-called radiation treatment plan often servesin the foregoing regards.

A radiation treatment plan typically comprises specified values for eachof a variety of treatment-platform parameters during each of a pluralityof sequential fields. Treatment plans for radiation treatment sessionsare often generated through a so-called optimization process. As usedherein, “optimization” will be understood to refer to improving acandidate treatment plan without necessarily ensuring that the optimizedresult is, in fact, the singular best solution. Such optimization oftenincludes automatically adjusting one or more treatment parameters (oftenwhile observing one or more corresponding limits in these regards) andmathematically calculating a likely corresponding treatment result toidentify a given set of treatment parameters that represent a goodcompromise between the desired therapeutic result and avoidance ofundesired collateral effects.

Formulating a radiation treatment plan typically includes determining adose. A Fourier transform dose calculator often serves to provide suchdose information. Unfortunately, when dealing with a heterogeneous body(such as lung tissue or other bodies containing air cavities), the dosecalculated by existing dose calculation methods (such asconvolution/superposition based dose calculation methods including butnot limited to kernel-based dose calculation methods such as Fouriertransform dose calculation methods) is typically overestimated. A dosecan be more accurately calculated using other approaches, but thoseother approaches can require considerably more time to achieve thedesired calculation. By contrast, convolution/superposition based dosecalculation methods are much faster and hence more desirable in apractical application setting.

BRIEF DESCRIPTION OF THE DRAWINGS

The above needs are at least partially met through provision of themethod and apparatus to a therapeutic body described in the followingdetailed description, particularly when studied in conjunction with thedrawings, wherein:

FIG. 1 comprises a block diagram as configured in accordance withvarious embodiments of these teachings;

FIG. 2 comprises a flow diagram as configured in accordance with variousembodiments of these teachings; and

FIG. 3 comprises a graph that accords with various embodiments of theseteachings.

Elements in the figures are illustrated for simplicity and clarity andhave not necessarily been drawn to scale. For example, the dimensionsand/or relative positioning of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of various embodiments of the present teachings. Also,common but well-understood elements that are useful or necessary in acommercially feasible embodiment are often not depicted in order tofacilitate a less obstructed view of these various embodiments of thepresent teachings. Certain actions and/or steps may be described ordepicted in a particular order of occurrence while those skilled in theart will understand that such specificity with respect to sequence isnot actually required. The terms and expressions used herein have theordinary technical meaning as is accorded to such terms and expressionsby persons skilled in the technical field as set forth above exceptwhere different specific meanings have otherwise been set forth herein.The word “or” when used herein shall be interpreted as having adisjunctive construction rather than a conjunctive construction unlessotherwise specifically indicated.

DETAILED DESCRIPTION

Generally speaking, these various embodiments support the development ofan optimized radiation treatment plan to effect radiation-basedtreatment of a patient's planning treatment volume. For the sake of anillustrative example these teachings can be carried out at least in partby an enabling control circuit. That control circuit may, or may not, bepart of an integrated circuit.

These teachings provide for facilitating the administration oftherapeutic radiation to a heterogeneous body, such as a heterogeneouspatient volume or phantom, using a radiation beam source. Moreparticularly, these teachings provide for determining a cross-sectionalsize of a radiation beam as corresponds to that radiation beam source.These teachings also provide for determining density informationcorresponding to the aforementioned heterogeneous body. These teachingsthen provide for generating a three-dimensional radiation dosecalculation for the heterogeneous body using a control circuitconfigured as a convolution/superposition based dose calculator using athree-dimensional energy-spreading kernel. By one approach, theseteachings provide for the calculator scaling total energy released permass as a function of both the cross-sectional size of the radiationbeam and the aforementioned density information.

By one approach, the calculator scales downwardly the total energyreleased per mass for portions of the body having a relatively lowerdensity and scales upwardly the total energy released per mass forportions of the body having a relatively higher density. This approachcan include using a scaling factor that is modeled as a function of aneffective beam size, beam energy, and density at a particular point inthe body.

By one approach, the aforementioned calculator can be further configuredto convolve scale total energy released per mass information at a giveninteraction site with a primary kernel (such as a water kernel) for areference density material.

These teachings will accommodate generating a radiation treatment planas a function, at least in part, of the aforementioned three-dimensionalradiation dose calculation and then administering therapeutic radiationto a corresponding heterogeneous patient volume per that radiationtreatment plan.

In existing convolution/superposition based dose calculation methods,the total energy released per mass is calculated according to an actualdensity distribution, with the total energy released per mass beingconvolved with a water kernel to obtain the deposited dose. Thisapproach, however, typically results in overdosing regions having adensity less than water. The present teachings can provide for scalingdown the total energy released per mass in lower-density regions by anappropriate factor before convolving the resultant total energy releasedper mass with a water kernel. In particular, these teachings can providefor modeling a corresponding scaling factor as a function of theeffective beam size, beam energy, and density at a particular point inthe heterogeneous body. This approach leads to more accurate resultswhile still retaining the relatively fast computation time oneordinarily associates with convolution/superposition based dosecalculation methods.

These and other benefits may become clearer upon making a thoroughreview and study of the following detailed description. Referring now tothe drawings, and in particular to FIG. 1 , an illustrative apparatus100 that is compatible with many of these teachings will now bepresented.

In this particular example, the enabling apparatus 100 includes acontrol circuit 101. Being a “circuit,” the control circuit 101therefore comprises structure that includes at least one (and typicallymany) electrically-conductive paths (such as paths comprised of aconductive metal such as copper or silver) that convey electricity in anordered manner, which path(s) will also typically include correspondingelectrical components (both passive (such as resistors and capacitors)and active (such as any of a variety of semiconductor-based devices) asappropriate) to permit the circuit to effect the control aspect of theseteachings.

Such a control circuit 101 can comprise a fixed-purpose hard-wiredhardware platform (including but not limited to an application-specificintegrated circuit (ASIC) (which is an integrated circuit that iscustomized by design for a particular use, rather than intended forgeneral-purpose use), a field-programmable gate array (FPGA), and thelike) or can comprise a partially or wholly-programmable hardwareplatform (including but not limited to microcontrollers,microprocessors, and the like). These architectural options for suchstructures are well known and understood in the art and require nofurther description here. This control circuit 101 is configured (forexample, by using corresponding programming as will be well understoodby those skilled in the art) to carry out one or more of the steps,actions, and/or functions described herein.

The control circuit 101 operably couples to a memory 102. This memory102 may be integral to the control circuit 101 (as when the memory 102and control circuit 101 are both included on a shared integratedcircuit) or can be physically discrete (in whole or in part) from thecontrol circuit 101 as desired. This memory 102 can also be local withrespect to the control circuit 101 (where, for example, both share acommon circuit board, chassis, power supply, and/or housing) or can bepartially or wholly remote with respect to the control circuit 101(where, for example, the memory 102 is physically located in anotherfacility, metropolitan area, or even country as compared to the controlcircuit 101).

In addition to optimization objectives information, patient geometryinformation, field geometry information, and so forth this memory 102can serve, for example, to non-transitorily store the computerinstructions that, when executed by the control circuit 101, cause thecontrol circuit 101 to behave as described herein. (As used herein, thisreference to “non-transitorily” will be understood to refer to anon-ephemeral state for the stored contents (and hence excludes when thestored contents merely constitute signals or waves) rather thanvolatility of the storage media itself and hence includes bothnon-volatile memory (such as read-only memory (ROM) as well as volatilememory (such as a dynamic random access memory (DRAM).)

By one optional approach the control circuit 101 also operably couplesto a user interface 103. This user interface 103 can comprise any of avariety of user-input mechanisms (such as, but not limited to, keyboardsand keypads, cursor-control devices, touch-sensitive displays,speech-recognition interfaces, gesture-recognition interfaces, and soforth) and/or user-output mechanisms (such as, but not limited to,visual displays, audio transducers, printers, and so forth) tofacilitate receiving information and/or instructions from a user and/orproviding information to a user.

In this illustrative example the control circuit 101 also operablycouples to a network interface 118 that communicatively couples to oneor more communication networks 119 (such as, but not limited to, theInternet). So configured the control circuit 101 can communicate withother elements (both within the apparatus 100 and external thereto, suchas one or more remote entities 120) via the network interface 118.Network interfaces, including both wireless and non-wireless platforms,are well understood in the art and require no particular elaborationhere.

By one approach, a computed tomography apparatus 106 and/or other non-CTimaging apparatus 107 as are known in the art can source some or all ofany desired patient-related imaging information.

In this illustrative example the control circuit 101 is configured toalso optionally output an optimized radiation treatment plan 113. Thisradiation treatment plan 113 typically comprises specified values foreach of a variety of treatment-platform parameters during each of aplurality of sequential fields. In this case the radiation treatmentplan 113 is generated through an optimization process. Variousnon-automated, automated, or partially-automated optimization processesspecifically configured to generate such a radiation treatment plan areknown in the art. As the present teachings are not overly sensitive toany particular selections in these regards, further elaboration in theseregards is not provided here except where particularly relevant to thedetails of this description.

By one approach the control circuit 101 can operably couple to aradiation treatment platform 114 that is configured to delivertherapeutic radiation 112 to a corresponding patient 104 in accordancewith the optimized radiation treatment plan 113. These teachings aregenerally applicable for use with any of a wide variety of radiationtreatment platforms. In a typical application setting the radiationtreatment platform 114 will include a radiation source 115. Theradiation source 115 can comprise, for example, a radio-frequency (RF)linear particle accelerator-based (linac-based) x-ray source, such asthe Varian Linatron M9. The linac is a type of particle accelerator thatgreatly increases the kinetic energy of charged subatomic particles orions by subjecting the charged particles to a series of oscillatingelectric potentials along a linear beamline, which can be used togenerate ionizing radiation (e.g., X-rays) 116 and high energyelectrons.

A typical radiation treatment platform 114 may also include one or moresupport apparatuses 110 (such as a couch) to support the patient 104during the treatment session, one or more patient fixation apparatuses111, a gantry or other movable mechanism to permit selective movement ofthe radiation source 115, and one or more beam-shaping apparatuses 117(such as jaws, multi-leaf collimators, and so forth) to provideselective beam shaping and/or beam modulation as desired. As theforegoing elements and systems are well understood in the art, furtherelaboration in these regards is not provided here except where otherwiserelevant to the description.

Referring now to FIG. 2 , a process 200 that can be carried out, forexample and at least in part, by the above-described control circuit 101will be presented.

At block 201, this process 200 provides for determining across-sectional size of a radiation beam as corresponds to a radiationbeam source 115. By one approach, this determination pertains to thecross-sectional size at the source. By another approach, thecross-sectional size of the beam may be referenced at a location otherthan at the source. Generally speaking, this cross-sectional size can bereferenced and understood with respect to a Cartesian reference system.That said, this process 200 will likely provide more beneficial resultswhen referencing an effective beam size in order to accommodatenon-rectangular cross-sections (including, for example, C-shapedcross-sections).

At block 202, this process 200 provides for determining densityinformation corresponding to a body that itself comprises at least oneof a heterogeneous patient volume and a phantom. (The ordinarily-skilledperson will understand that so-called phantoms are often used inclinical work for making measurements as a useful substitute for anactual measure of a volume within a patient (such as a lung). Phantomsare therefore typically comprised of a material having requisiteproperties, such as a similar density, to the actual patient targetvolume and/or a patient volume between the radiation source and thetarget volume itself.) It will be understood that a heterogeneouspatient volume may comprise a target volume (for example, a tumor to beirradiated) or may comprise, for example, an organ at risk (including,but certainly not limited to, healthy lung tissue).

The determined density information may comprise mass density. Theseteachings are flexible in practice, however, and will accommodate otherapproaches. For example, the density information may pertain instead tosuch things as electron density.

At block 203, this process 200 provides for generating athree-dimensional radiation dose calculation for the heterogeneous bodyusing, for example, the aforementioned control circuit 101 configured asa convolution/superposition based dose calculator that uses athree-dimensional energy-spreading kernel. By one approach theseteachings provide for configuring this calculator to scale the totalenergy released per mass as a function of both the aforementioneddetermined cross-sectional size of the radiation beam and theaforementioned determined density information.

The aforementioned scaling may comprise, for example, scaling downwardlythe total energy released per mass for portions of the body having arelatively lower density while scaling upwardly the total energyreleased per mass having a relatively higher density. By anotherapproach, if desired, these teachings may provide for only scalingdownwardly when necessary or scaling upwardly when necessary. Theaforementioned scaling can include using a scaling factor that ismodeled as a function of an effective beam size, beam energy, anddensity at a particular point in the aforementioned heterogeneous body.

With reference to optional block 204, these teachings will alsoaccommodate, if desired, further configuring the aforementionedcalculator to convolve scaled total energy released per mass informationat a given interaction site with a primary kernel for a referencedensity material (such as, for example, water). So configured, theseteachings permit using convolution/superposition based dose calculationmethods in heterogeneous bodies in conjunction with a water kernelnotwithstanding the presence of portions of the body having a densityless than water.

Without intending to suggest any particular limitations as regards theseteachings, the following equations offer an illustrative example asregards the foregoing. In these equations, L represents the beam size,X_(eff) and Y_(eff) refer to the effective width and height of the beam,ρ represents the determined density, S represents the scaling factor, rrepresents a Cartesian vector, and c1 through c3 are constants (wherethose skilled in the art will recognize that these constants representparameters selected to match particular dose calculations; for the sakeof this illustrative example, c1=0.84, c2=0.28, and c3=0.12). In thisexample scaling factor S is modeled as a function of the beam size andthe density. The graph 300 depicted in FIG. 3 presents scaling factorsfor a variety of items including lung tissue, cork, and air.L=√{square root over (X_(eff) Y _(eff))}S(L,ρ(r))=1-31 (1−ρ(r))(c ₁ e ^(−c2ρ(r)L) +c ₃)T _(scaled)(r)=T(r)S(L,ρ(r))

The calculated result, T_(scaled), constitutes the scaled total energyreleased per mass. That calculated value can then be utilized pursuantto ordinary prior art approaches when calculating dosing.

Although the time required to effect necessary calculations presumed bythese teachings are essentially equivalent to traditional fast Fouriertransform dose calculations, the applicant has determined that theaccuracy achieved by these teachings is generally comparable to theanisotropic analytical algorithmic approach that ordinarily requiresconsiderably more time than fast Fourier transform dose calculations. Byretaining use of kernel uniformity (by, for example, using the waterkernel), these teachings essentially leave the application of the fastFourier transform unaffected and only introduce an additional smallcomputational overhead (determined by the applicant to be about 10%) toaccommodate the aforementioned scaling of the total energy released permass value(s). Accordingly, those skilled in the art will recognize thatthese teachings are readily applicable for real-world applicationsettings such as inverse treatment planning.

At optional block 205, this process 200 will accommodate generating aradiation treatment plan 113 as a function, at least in part, of theaforementioned three-dimensional radiation dose calculation(s). Atoptional block 206, this process 200 will also accommodate administeringtherapeutic radiation to a heterogeneous patient volume per theaforementioned radiation treatment plan 113 using, for example, theaforementioned radiation treatment platform 114.

Those skilled in the art will recognize that a wide variety ofmodifications, alterations, and combinations can be made with respect tothe above-described embodiments without departing from the scope of theinvention, and that such modifications, alterations, and combinationsare to be viewed as being within the ambit of the inventive concept.

What is claimed is:
 1. A method to facilitate the administration oftherapeutic radiation to a heterogeneous patient volume using aradiation beam source, the method comprising: determining across-sectional size of a radiation beam as corresponds to the radiationbeam source; determining density information corresponding to a bodycomprising at least one of a phantom and the heterogeneous patientvolume; generating a three-dimensional radiation dose calculation forthe body using a control circuit configured as aconvolution/superposition based dose calculator using athree-dimensional energy-spreading kernel, wherein the calculator scalestotal energy released per mass as a function of both the cross-sectionalsize of the radiation beam and the density information.
 2. The method ofclaim 1 wherein the heterogeneous patient volume comprises at least oneof: a patient target volume; and an organ at risk.
 3. The method ofclaim 2 wherein the patient target volume comprises, at least in part,lung tissue.
 4. The method of claim 1 wherein the calculator scalesdownwardly the total energy released per mass for portions of the bodyhaving a relatively lower density and scales upwardly the total energyreleased per mass for portions of the body having a relatively higherdensity.
 5. The method of claim 1 wherein the calculator is furtherconfigured to convolve scaled total energy released per mass informationat a given interaction site with a primary kernel for a referencedensity material.
 6. The method of claim 1 wherein the calculator isconfigured to scale the total energy released per mass by using ascaling factor that is modeled as a function of an effective beam sizeand density at a particular point in the body.
 7. The method of claim 1further comprising: by the control circuit: generating a radiationtreatment plan as a function, at least in part, of the three-dimensionalradiation dose calculation.
 8. The method of claim 7 further comprising:administering therapeutic radiation to the heterogeneous patient volumeper the radiation treatment plan.
 9. An apparatus to facilitate theadministration of therapeutic radiation to a heterogeneous patientvolume using a radiation beam source, the apparatus comprising: a memoryhaving stored therein: a cross-sectional size of a radiation beam ascorresponds to the radiation beam source; and density informationcorresponding to a body comprising at least one of a phantom and theheterogeneous patient volume; a control circuit operably coupled to thememory and configured as a convolution/superposition based dosecalculator using a three-dimensional energy-spreading kernel to generatea three-dimensional radiation dose calculation for the heterogeneouspatient volume, wherein the calculator scales total energy released permass as a function of both the cross-sectional size of the radiationbeam and the density information.
 10. The apparatus of claim 9 whereinthe heterogeneous patient volume comprises at least one of: a patienttarget volume; and an organ at risk.
 11. The apparatus of claim 10wherein the patient target volume comprises, at least in part, lungtissue.
 12. The apparatus of claim 9 wherein the calculator scalesdownwardly the total energy released per mass for portions of the bodyhaving a relatively lower density and scales upwardly the total energyreleased per mass for portions of the body having a relatively higherdensity.
 13. The apparatus of claim 9 wherein the calculator is furtherconfigured to convolve scaled total energy released per mass informationat a given interaction site with a primary kernel for a referencedensity material.
 14. The apparatus of claim 9 wherein the calculator isconfigured to scale the total energy released per mass by using ascaling factor that is modeled as a function of an effective beam sizeand density at a particular point in the body.
 15. The apparatus ofclaim 9 wherein the control circuit is further configured to: generate aradiation treatment plan as a function, at least in part, of thethree-dimensional radiation dose calculation.
 16. The apparatus of claim15 further comprising: a radiation treatment platform operably coupledto the control circuit and configured to administer therapeuticradiation to the heterogeneous patient volume per the radiationtreatment plan.
 17. A non-transitory memory having instructions storedtherein, which instructions, when executed by a control circuit, causethe control circuit to: determine a cross-sectional size of a radiationbeam as corresponds to a radiation beam source; determine densityinformation corresponding to a body comprising at least one of a phantomand a heterogeneous patient volume; serve as a convolution/superpositionbased dose calculator using a three-dimensional energy-spreading kernelto generate a three-dimensional radiation dose calculation for theheterogeneous patient volume, wherein the calculator scales total energyreleased per mass as a function of both the cross-sectional size of theradiation beam and the density information.
 18. The non-transitorymemory of claim 17 wherein the calculator is configured to scaledownwardly the total energy released per mass for portions of the bodyhaving a relatively lower density and scale upwardly the total energyreleased per pass for portions of the body having a relatively higherdensity.
 19. The non-transitory memory of claim 17 wherein thecalculator is further configured to convolve scaled total energyreleased per mass information at a given interaction site with a primarykernel for a reference density material.
 20. The non-transitory memoryof claim 17 wherein the calculator is configured to scale the totalenergy released per mass by using a scaling factor that is modeled as afunction of an effective beam size and density at a particular point inthe body.